The present invention relates to a decorative component for a vehicle having a radar device.
Conventionally, some vehicles are equipped with a radar device located on the back of the front grille for measuring the distance with another vehicle or an obstacle by using radar waves. If a decorative component such as a metal emblem is located in the path of radar waves transmitted from the radar device, the radar waves are interfered by the component. This causes the radar device to function improperly.
Accordingly, for example, Japanese Laid-Open Patent Publication No. 2002-135030 discloses a vehicle decorative component that includes a back coating plate made of a material transparent to radar waves, an outer surface coating plate made of an optically transparent material that is also transparent to radar waves, and a metal film made of indium located between the back coating plate and the outer surface coating plate. The indium film is transparent to radar waves. Since the vehicle decorative component disclosed in Japanese Laid-Open Patent Publication No. 2002-135030 includes a metal film made of indium, the component has radar wave transparency as well as a metallic appearance.
Japanese Laid-Open Patent Publication No. 2004-309322 discloses a vehicle decorative component having a two-layer structure in which a substantially optically transparent protective layer and a back layer that are adhered to each other. In the vehicle decorative component of Japanese Laid-Open Patent Publication No. 2004-309322, the refractive index of the back layer is less than the refractive index of the protective layer, and protrusions and recesses are formed between the protective layer and the back layer. Although the decorative component of the publication No. 2004-309322 has no metal layer, light is reflected by the protrusions and recesses, which gives the component a metallic appearance.
Since the metal film of Japanese Laid-Open Patent Publication No. 2002-135030 is formed of a special metal, or indium, which has a high transparency to radar waves, the manufacturing costs are increased. In the vehicle decorative component of the publication No. 2004-309322, the refractive index of the back layer is less than that of the protective layer. Thus, the interface between the back layer and the protective layer is likely to refract and reflect radar waves. Such refractions and reflections of radar waves attenuate the intensity of the radar waves. As a result, the radar waves cannot readily pass through the decorative component of the publication No. 2004-309322.